Light-emitting diodes transformational

By Forrest Mims :
July 24, 2013
: Updated: July 25, 2013 10:18am

Take a look at how LED lights (light-emitting diodes) are being used today.

This tiny but powerful flashlight owes its brilliance to a light-emitting diode that emits a blinding beam of white light.

Photo By MANJUNATH KIRAN/AFP/Getty Images

Dancers wearing dressed embedded with LED lights perform amidst a laser beams held as part of a fashion show organised by the Indian ethnic fashion garment house 'Rajguru Rise,' in Bangalore on July 23, 2013. Getty Images

Photo By Courtesy photo

A computerized LED light sculpture illuminates the crown and the southern side of the Robert B. Green Clinical Pavilion, University Health System in downtown San Antonio.

The H-E-B Christmas tree boasts 10,000 white LED lights in front of the Alamo.

Photo By Robin Jerstad/For the Express-News

LED lights for horse-drawn carriages are a common site around the Alamo.

Photo By JERRY LARA/San Antonio Express-News

People line up to board the 100-foot Giant Wheel on the first day of the Fiesta Carnival by the Alamodome, Wednesday, April 18, 2012. The carnival is getting greener with LED lights on some of the ride and recycling trash cans alongside regular trash cans. With the change to LED lights, the amp usage for the Giant Wheel went from 400 to 37 amps, said Wade Shows President Frank Zaitshik.

Photo By AP

In this Nov. 30, 2011 photo, Corpus Christi, Texas resident were treated to sneak preview of the new lights along the Harbor Bridge, as the city tested its new bridge lights in preparation of Sunday, Dec 4, 2012 official unveiling of a new lighting system. The new programmable $2.2 million lighting system, include 950 LED lights that will cover the bridge in a array of colors and patterns.(AP Photo/Corpus Christi Caller-Times, Todd Yates)

Photo By MOHD RASFAN/Stringer

A worker inspects the dragon lantern decoration with energy-saving LED lights at the Fo Guang Shan Dong Zen temple in Jenjarom, on January 16, 2012. Getty Images

Photo By Louis Lanzano/Associated Press

A blue LED light is used to quickly dry nail polish on a model backstage before the showing of the Naeem Khan Spring, 2013 collection during Fashion Week. (AP Photo/Louis Lanzano)

Photo By John Hart/Associated Press

A gallery assistant with the Madison Museum of Contemporary Art in Madison, Wis., sweeps the floor in front of an LED light panel by American artist Leo Villareal at the museum. AP Photo

It seems like only yesterday when I hitchhiked from Texas A&M University to Dallas in March 1966 to meet Ed Bonin at Texas Instruments. Bonin showed me a cylinder no larger than his thumb. When he pressed a button at one end of the device, red light emerged from a tiny crystal installed in the opposite end.

This was a magical moment. It was amazing to see light emitted by a crystal the size of a grain of salt powered by a small flashlight battery.

The crystal in Bonin's miniature light source was a light-emitting diode, or LED, a device that emits light when electricity passes from one region of the crystal to another.

In 1961 Texas Instruments developed powerful LEDs that emitted invisible near-infrared light just beyond the red that we can see. These LEDs eventually evolved into the infrared light sources used in TV remote controllers, intruder alarms and military night-vision devices.

Meanwhile, Nick Holonyak Jr. had a clever idea. Holonyak worked for General Electric, the company cofounded by Thomas Edison in 1892. Edison developed the first commercially successful incandescent electric light, and in 1962 Holonyak followed in Edison's footsteps by developing the first practical LED that emitted visible light.

In 1963 Holonyak became a professor at the University of Illinois, where he trained students who went on to develop improved LEDs and lasers.

Holonyak's pioneering LED work led to the development of many kinds of red, orange, yellow and green LED indicators and readouts that displayed numbers and letters. Missing from the mix was blue, until Japanese scientist Shuji Nakamura invented the first practical blue LED in 1994.

The blue LED completed the spectrum and permitted the development of giant display screens and advertising signs.

The white LED arrived when blue LEDs were coated with a phosphor that glows green and red when illuminated by blue light. Mixing these colors produces white light.

Today LEDs are everywhere. The monitor of the computer into which this column was typed is illuminated by LEDs. Many traffic signals and car tail lights use bright LEDs. Flashlights that employ white LEDs are much brighter than incandescent flashlights and use much less power. You can now buy long-lasting LED lamps for household use.

Holonyak received the National Medal of Science, the National Medal of Technology and various other awards for his innovative developments of LEDs and lasers. You can learn much more about this remarkable inventor at the website devoted to the 50th anniversary of his invention of the LED: www.led50years.illinois.edu/about.html. Some of the facts in this column were provided by this site.

Forrest Mims, an amateur scientist whose research has appeared in leading scientific journals, was named one of the “50 Best Brains in Science” by Discover Magazine. His science is featured at www.forrestmims.org. Email him at forrest.mims@ieee.org.